<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>flex布局-01</title>
		<style>
			div{
				font-size: 16px;
				width: 10em;
				height: 10em;
				background-color: skyblue;
				display: flex;
				margin: 2em;
				background-image: linear-gradient(transparent 50%, 
				darkgreen cale(50% + 1px), transparent cale(50% + 1px)),
				linear-gradient(to right, transparent 50%, 
				darkgreen cale(50% + 1px), transparent cale(50% + 1px));
				background-size: 10em, 10em;
			}
			div span{
				width: 7em;
				height: 7em;
				background-color: hsl(0, 100%, 72%, 0.8);
				border-radius: 50%;
			}
			div:nth-child(1){
				align-items: center;
			}
			div:nth-child(2){
				justify-content: center;
			}
			div:nth-child(3){
				align-items: center;
				justify-content: center;
			}
		</style>
	</head>
	<body>
		<div>
			<span></span>
		</div>
		<div>
			<span></span>
		</div>
		<div>
			<span></span>
		</div>
	</body>
</html>
